A framework for good biofilm reactor modeling practice (GBRMP).

A researcher or practitioner can employ a biofilm model to gain insight into what controls the performance of a biofilm process and for optimizing its performance. While a wide range of biofilm-modeling platforms is available, a good strategy is to choose the simplest model that includes sufficient components and processes to address the modeling goal. In most cases, a one-dimensional biofilm model provides the best balance, and good choices can range from hand-calculation analytical solutions, simple spreadsheets, and numerical-method platforms.

Evaluating death and activity decay of Anammox bacteria during anaerobic and aerobic starvation.

The decreased activity (i.e. decay) of anaerobic ammonium oxidation (Anammox) bacteria during starvation can be attributed to death (i.

Growth yield and selection of nosZ clade II types in a continuous enrichment culture of N O respiring bacteria.

Nitrous oxide (N O) reducing microorganisms may be key in the mitigation of N O emissions from managed ecosystems. However, there is still no clear understanding of the physiological and bioenergetic implications of microorganisms possessing either of the two N O reductase genes (nosZ), clade I and the more recently described clade II type nosZ. It has been suggested that organisms with nosZ clade II have higher growth yields and a lower affinity constant (K ) for N O.

Life on NO: deciphering the ecophysiology of NO respiring bacterial communities in a continuous culture.

Reduction of the greenhouse gas NO to N is a trait among denitrifying and non-denitrifying microorganisms having an NO reductase, encoded by nosZ. The nosZ phylogeny has two major clades, I and II, and physiological differences among organisms within the clades may affect NO emissions from ecosystems. To increase our understanding of the ecophysiology of NO reducers, we determined the thermodynamic growth efficiency of NO reduction and the selection of NO reducers under NO- or acetate-limiting conditions in a continuous culture enriched from a natural community with NO as electron acceptor and acetate as electron donor.

Effective role of medium supplementation in microalgal lipid accumulation.

The present study investigated the interaction between starch and lipid accumulation in a green microalgae enrichment culture. The objective was to optimize the lipid content by manipulation of the medium in regular batch culture. Two medium designs were evaluated: First a high ortho-P concentration with vitamin supplementary (Pi-vitamins supplemented medium), second normal growth medium (control).

Exploring microbial N O reduction: a continuous enrichment in nitrogen free medium.

N O is a potent greenhouse gas, but also a potent electron acceptor. In search of thermodynamically favourable - yet undescribed - metabolic pathways involving N O reduction, we set up a continuous microbial enrichment, inoculated with activated sludge, fed with N O as the sole electron acceptor and acetate as an electron donor. A nitrogen-free mineral medium was used with the intention of creating a selective pressure towards organisms that would use N O directly as source of nitrogen for cell synthesis.

Enrichment of PHA-producing bacteria under continuous substrate supply.

To enrich polyhydroxyalkanoate (PHA) producing microbial communities, generally, a feast-famine regime is applied. Here we investigated the impact of continuous substrate feeding on the enrichment of PHA-producing bacteria in two sequencing batch reactors (SBRs). In the first reactor, the substrate (acetate) was dosed continuously and Zoogloea sp.

Stability of aerobic granules during long-term bioreactor operation.

Aerobic granular sludge technology has been extensively studied over the past 20 years and is regarded as the upcoming new standard for biological treatment of domestic and industrial wastewaters. Aerobic granules (AG) are dense, compact, self-immobilized microbial aggregates that allow better sludge-water separation and thereby higher biomass concentrations in the bioreactor than conventional activated sludge aggregates. This brings potential practical advantages in terms of investment cost, energy consumption and footprint.

Sludge reduction by ozone: Insights and modeling of the dose-response effects.

Applying ozone to the return flow in an activated sludge (AS) process is a way for reducing the residual solids production. To be able to extend the activated sludge models to the ozone-AS process, adequate prediction of the tri-atoms effects on the particulate COD fractions is needed. In this study, the biomass inactivation, COD mineralization, and solids dissolution were quantified in batch tests and dose-response models were developed as a function of the reacted ozone doses (ROD).

Impact of phosphate limitation on PHA production in a feast-famine process.

Double-limitation systems have shown to induce polyhydroxyalkanoates (PHA) production in chemostat studies limited in e.g. carbon and phosphate.

Fermentative Bacteria Influence the Competition between Denitrifiers and DNRA Bacteria.

Denitrification and dissimilatory reduction to ammonium (DNRA) are competing nitrate-reduction processes that entail important biogeochemical consequences for nitrogen retention/removal in natural and man-made ecosystems. The nature of the available carbon source and electron donor have been suggested to play an important role on the outcome of this microbial competition. In this study, the influence of lactate as fermentable carbon source on the competition for nitrate was investigated for varying ratios of lactate and nitrate in the influent (Lac/N ratio).

Gradual adaptation to salt and dissolved oxygen: Strategies to minimize adverse effect of salinity on aerobic granular sludge.

Salinity can affect the performance of biological wastewater treatment in terms of nutrient removal. The effect of salt on aerobic granular sludge (AGS) process in terms of granulation and nutrient removal was examined in this study. Experiments were conducted to evaluate the effect of salt (15 g/L NaCl) on granule formation and nutrient removal in AGS system started with flocculent sludge and operated at DO of 2.

Enrichment of highly settleable microalgal consortia in mixed cultures for effluent polishing and low-cost biomass production.

Microalgae cultivation is a promising technology for integrated effluent polishing and biofuel production, but poor separability of microalgal cells hinders its industrial application. This study intended to selectively enrich settleable microalgal consortia in mixed culture by applying "wash-out" pressure, which was realized by controlling settling time (S) and volume exchange ratio (VER) in photo-SBRs. The results demonstrated that highly settleable microalgal consortia (settling efficiency>97%; SVI = 17-50 mL/g) could be enriched from indigenous algal cultures developed in WWTP's effluent.

Effect of temperature on NO emissions from a highly enriched nitrifying granular sludge performing partial nitritation of a low-strength wastewater.

In the race to achieve a sustainable urban wastewater treatment plant, not only the energy requirements have to be considered but also the environmental impact of the facility. Thus, nitrous oxide (NO) emissions are a key-factor to pay attention to, since they can dominate the total greenhouse gases emissions from biological wastewater treatment. In this study, NO production factors were calculated during the operation of a granular sludge airlift reactor performing partial nitritation treating a low-strength synthetic influent, and furthermore, the effect of temperature on NO production was assessed.

Dynamic modeling of nutrient removal by a MBR operated at elevated temperatures.

The process performance of a MBR operated on municipal sewage at elevated temperatures was evaluated by dynamic modeling. The enhanced biological phosphorus removal (EBPR) performance varied from 40% to 95% with process temperature ranging from 24 to 38 °C. The respective maximum substrate uptake rate (q) was estimated at 1.

The acid soluble extracellular polymeric substance of aerobic granular sludge dominated by Defluviicoccus sp.

A new acid soluble extracellular polymeric substance (acid soluble EPS) was extracted from an acetate fed aerobic granular sludge reactor operated at 35 °C. Acid soluble EPS dominated granules exhibited a remarkable and distinctive tangled tubular morphology. These granules are dominated by Defluviicoccus Cluster II organisms.

Discovery of extremely halophilic, methyl-reducing euryarchaea provides insights into the evolutionary origin of methanogenesis.

Methanogenic archaea are major players in the global carbon cycle and in the biotechnology of anaerobic digestion. The phylum Euryarchaeota includes diverse groups of methanogens that are interspersed with non-methanogenic lineages. So far, methanogens inhabiting hypersaline environments have been identified only within the order Methanosarcinales.

Effects of electron acceptors on sulphate reduction activity in activated sludge processes.

The concentration of sulphate present in wastewater can vary from 10 to 500 mg SO/L. During anaerobic conditions, sulphate is reduced to sulphide by sulphate-reducing bacteria (SRB). Sulphide generation is undesired in wastewater treatment plants (WWTPs).

Microscale Quantitative Analysis of Polyhydroxybutyrate in Prokaryotes Using IDMS.

Poly(3-hydroxybutyrate) (PHB) is an interesting biopolymer for replacing petroleum-based plastics, its biological production is performed in natural and engineered microorganisms. Current metabolic engineering approaches rely on high-throughput strain construction and screening. Analytical procedures have to be compatible with the small scale and speed of these approaches.

Porosity of spacer-filled channels in spiral-wound membrane systems: Quantification methods and impact on hydraulic characterization.

The porosity of spacer-filled feed channels influences the hydrodynamics of spiral-wound membrane systems and impacts the overall performance of the system. Therefore, an exact measurement and a detailed understanding of the impact of the feed channel porosity is required to understand and improve the hydrodynamics of spiral-wound membrane systems applied for desalination and wastewater reuse. The objectives of this study were to assess the accuracy of porosity measurement techniques for feed spacers differing in geometry and thickness and the consequences of using an inaccurate method on hydrodynamic predictions, which may affect permeate production.

Role of nitrite in the competition between denitrification and DNRA in a chemostat enrichment culture.

Denitrification and dissimilatory nitrate reduction to ammonium (DNRA) are two microbial processes that compete for oxidized nitrogen compounds in the environment. The objective of this work was to determine the role of nitrite versus nitrate as terminal electron acceptor on the competition between DNRA and denitrification. Initially, a mixed culture chemostat was operated under nitrate limitation and performed DNRA.

Cooperation between Candidatus Competibacter and Candidatus Accumulibacter clade I, in denitrification and phosphate removal processes.

Although simultaneous P-removal and nitrate reduction has been observed in laboratory studies as well as full-scale plants, there are contradictory reports on the ability of PAO I to efficiently use nitrate as electron acceptor. Such discrepancy could be due to other microbial groups performing partial denitrification from nitrate to nitrite. The denitrification capacities of two different cultures, a highly enriched PAO I and a PAO I-GAO cultures were assessed through batch activity tests conducted before and after acclimatization to nitrate.

Improving the accuracy of granular sludge and biofilm reactor simulations in Aquasim through artificial diffusion.

Aquasim is public-domain and user-friendly software that is widely used for biofilm modeling. The program uses built-in process unit blocks, such as biofilm and mixed compartments. In the literature, often several of these compartments are linked with artificial advective flows to represent a single physical well-mixed system, such as a granular sludge reactor.

From biofilm ecology to reactors: a focused review.

Biofilms are complex biostructures that appear on all surfaces that are regularly in contact with water. They are structurally complex, dynamic systems with attributes of primordial multicellular organisms and multifaceted ecosystems. The presence of biofilms may have a negative impact on the performance of various systems, but they can also be used beneficially for the treatment of water (defined herein as potable water, municipal and industrial wastewater, fresh/brackish/salt water bodies, groundwater) as well as in water stream-based biological resource recovery systems.